Three in12c: Row Limiting, PL/SQL With SQL and Temporal Validity von Christian Antognini an DOAG 2014

1. 2014 © Trivadis
BASEL BERN BRUGG LAUSANNE ZUERICH DUESSELDORF FRANKFURT A.M. FREIBURG I.BR. HAMBURG MUNICH STUTTGART VIENNA
Three in 12c: Row Limiting, PL/SQL WITH SQL and Temporal Validity
DOAG 2014, Nürnberg (DE) Christian Antognini
18 November 2014
Three in 12c: Row Limiting, PL/SQL WITH SQL and Temporal Validity
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2. 2014 © Trivadis
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Three in 12c: Row Limiting, PL/SQL WITH SQL and Temporal Validity
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@ChrisAntognini
Senior principal consultant, trainer and partner at Trivadis in Zurich (CH)
christian.antognini@trivadis.com
http://antognini.ch
Focus: get the most out of Oracle Database
Logical and physical database design
Query optimizer
Application performance management
Author of Troubleshooting Oracle Performance (Apress, 2008/2014)
OakTable Network, Oracle ACE Director

3. 2014 © Trivadis
1.Native Support for Top-N Queries
2.PL/SQL in SQL Statements
3.Temporal Validity
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Three in 12c: Row Limiting, PL/SQL WITH SQL and Temporal Validity
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AGENDA

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Three in 12c: Row Limiting, PL/SQL WITH SQL and Temporal Validity
Native Support for Top-N Queries
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The SELECT statement has been enriched by the ROW_LIMITING_CLAUSE
Based on SQL:2011
Absolute top-N as well as percent top-N queries are possible
Absolute OFFSET may be declared
TIES handling is supported
Data should be ordered to get a decent top-N result
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ROW_LIMITING_CLAUSE

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Top-N Rows
SELECT first_name, last_name, salary FROM hr.employees ORDER BY salary DESC FETCH FIRST 5 ROWS ONLY
FIRST_NAME LAST_NAME SALARY -------------------- ------------------------- ---------- Steven King 24000 Neena Kochhar 17000 Lex De Haan 17000 John Russell 14000 Karen Partners 13500
ROW | ROWS can be used interchangeably

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Absolute Offset
SELECT first_name, last_name, salary FROM hr.employees ORDER BY salary DESC OFFSET 5 ROWS FETCH NEXT 5 ROWS ONLY
FIRST_NAME LAST_NAME SALARY -------------------- ------------------------- ---------- Michael Hartstein 13000 Nancy Greenberg 12000 Shelley Higgins 12000 Alberto Errazuriz 12000 Lisa Ozer 11500
FIRST | NEXT can be used interchangeably

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Three in 12c: Row Limiting, PL/SQL WITH SQL and Temporal Validity
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Top Percent Rows
SELECT first_name, last_name, salary FROM hr.employees ORDER BY salary DESC FETCH FIRST 5 PERCENT ROWS ONLY
FIRST_NAME LAST_NAME SALARY -------------------- ------------------------- ---------- Steven King 24000 Neena Kochhar 17000 Lex De Haan 17000 John Russell 14000 Karen Partners 13500 Michael Hartstein 13000
The number of rows returned is always a “ceiled” value in percent

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Also SQL:2011 doesn’t have it
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No Percent Offset
SELECT first_name, last_name, salary FROM hr.employees ORDER BY salary DESC OFFSET 5 PERCENT ROWS FETCH NEXT 5 PERCENT ROWS ONLY
ORA-00905: missing keyword

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Use WITH TIES to specify how to handle equalities at the edge of the row set
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Ties Handling
SELECT first_name, last_name, salary FROM hr.employees ORDER BY salary DESC FETCH FIRST 1 PERCENT ROWS ONLY
FIRST_NAME LAST_NAME SALARY -------------------- ------------------------- ---------- Steven King 24000 Neena Kochhar 17000

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Use WITH TIES to specify how to handle equalities at the edge of the row set
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Ties Handling
SELECT first_name, last_name, salary FROM hr.employees ORDER BY salary DESC FETCH FIRST 1 PERCENT ROWS WITH TIES
FIRST_NAME LAST_NAME SALARY -------------------- ------------------------- ---------- Steven King 24000 Neena Kochhar 17000 Lex De Haan 17000

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Also SQL:2011 doesn’t have it
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No Offset with Ties Handling
SELECT first_name, last_name, salary FROM employees ORDER BY salary DESC OFFSET 2 ROWS WITH TIES FETCH NEXT 1 PERCENT ROWS WITH TIES
ORA-00933: SQL command not properly ended

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Every implementation of a top-N query has to order the result set
Taking advantage of an index is also possible
Either the WINDOW SORT or WINDOW SORT PUSHED RANK are used
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Performance
----------------------------------------------
| Id | Operation | Name |
----------------------------------------------
| 0 | SELECT STATEMENT | |
| 1 | VIEW | |
| 2 | WINDOW SORT PUSHED RANK| |
| 3 | TABLE ACCESS FULL | EMPLOYEES |
----------------------------------------------

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Top-N queries are easier using ROW_LIMITING_CLAUSE
No need to use inline views with RANK() / DENSE_RANK() / ROW_NUMBER() to determine the rank of a row
No need to use nested inline views using ORDER BY, ROWNUM
Not being able to specify a percent OFFSET and an OFFSET with TIES might be a problem for paginating issues
But who does a paginating where the size of the returned dataset is unknown due to a per cent based specifications or an unknown number of ties?
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Assessment

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Three in 12c: Row Limiting, PL/SQL WITH SQL and Temporal Validity
PL/SQL in SQL Statements
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It is possible to define PL/SQL functions and procedures within a SQL statement
They are only accessible inside this SQL statement
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New WITH Clause Feature
WITH FUNCTION round2five (in_amount NUMBER) RETURN NUMBER IS BEGIN RETURN ROUND(in_amount*20)/20; END; SELECT last_name, first_name, salary , round2five(salary * 1.3131573) as new_sal_rounded FROM hr.employees WHERE ROWNUM <= 15

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More than one function/procedure may be defined
Functions/procedures may access functions/procedures defined earlier within the same WITH clause
Functions/procedures have to be defined prior to subquery factoring clause(s)
Functions/procedures may be accessed by the subquery factoring clause(s)
Functions/procedures specified in a WITH clause have priority over schema based functions/procedures sharing the same name
But not over SYS functions like USER/SYSDATE
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Options and Rules (1)

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If the function/procedure declaration is not in a top level SELECT statement or is not part of a SELECT statement at all then the WITH_PLSQL hint has to be used
Can be used in views
AUTONOMOUS_TRANSACTION possible
RESULT_CACHE is not supported in WITH clause functions
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Options and Rules (2)

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Example – Function with Exception Handler
WITH FUNCTION is_numeric (in_value IN VARCHAR2) RETURN NUMBER IS l_number number; BEGIN l_number := to_number(in_value); return 1; EXCEPTION WHEN value_error then return -1; END; ...

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Example – Usage Within a View
CREATE OR REPLACE VIEW employee_view AS WITH FUNCTION get_manager_formatted (in_manager_id IN NUMBER) RETURN VARCHAR2 DETERMINISTIC IS ...
SELECT * FROM employee_view WHERE rownum <= 15;

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Example – AUTONOMOUS_TRANSACTION
CREATE OR REPLACE VIEW employee_view AS WITH FUNCTION track_salary_access (in_rowid IN ROWID ,in_salary IN NUMBER) RETURN NUMBER IS PRAGMA AUTONOMOUS_TRANSACTION; BEGIN INSERT INTO employee_log (row_id) VALUES (in_rowid); COMMIT; RETURN in_salary; END; SELECT employee_id, first_name, last_name , track_salary_access(rowid, salary) salary FROM hr.employees;

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Do not expect major differences
The code doesn’t run in the SQL engine!
WITH clause program units might be faster than schema-based program units
Only parameter passing was optimized
Equivalent performance can be achieved with schema-based program units by using the UDF pragma
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Performance

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Cool stuff
Whenever you use a function/procedure at more than one place, you should create a schema object to keep it maintainable
SQL Developer 4.0.x does support this feature
SQL*Plus prior to 12c does not support this feature
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Limitations / Assessment

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Three in 12c: Row Limiting, PL/SQL WITH SQL and Temporal Validity
Temporal Validity
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Total Recall (System Time)
Temporal Validity (Business Time)
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Temporal Validity versus Total Recall (FBDA)

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Total Recall (System Time)
Previous and current states
Backdated changes are not possible1)
Future changes are not possible1)
Only system time supported
Temporal Validity (Business Time)
Previous, current and future states
Backdated changes are possible
Future changes are possible
Multiple valid time periods supported
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Temporal Validity versus Total Recall (FBDA)
1) at least not as part of standard DML

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Temporal Validity – Period, Semantics and Granularity
1981-02-20
2014-01-01
2015-04-01
1981-02-20 00:00:00
2014-01-01 00:00:00
2015-04-01 00:00:00
1981-02-20
00:00:00.000000
2014-01-01
00:00:00.000000
2015-04-01
00:00:00.000000
Start
End
CHICAGO
Start
End
SAN FRANCISCO

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valid_time_column is the name of temporal period
virtual and hidden
default prefix for start_time_column and end_time_column
start_time_column and end_time_column (NULL = )
hidden by default
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CREATE TABLE Enhancements

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ALTER TABLE Enhancements
ALTER TABLE dept ADD (vt_start DATE, vt_end DATE, PERIOD FOR vt (vt_start, vt_end))

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Visible Period Start and End Columns
SQL> SELECT * FROM dept;
DEPTNO DNAME LOC VT_START VT_END
---------- -------------- ------------- ---------- ----------
10 ACCOUNTING NEW YORK
20 RESEARCH DALLAS
30 SALES CHICAGO
40 OPERATIONS BOSTON

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Hidden, Virtual Column
SQL> SELECT column_name, data_type, data_length
, hidden_column, virtual_column
FROM user_tab_cols
WHERE table_name = 'DEPT' AND column_name LIKE 'VT%';
COLUMN_NAME DATA_TYPE DATA_LENGTH HIDDEN_COLUMN VIRTUAL_COLUMN
----------- --------- ----------- ------------- --------------
VT NUMBER 22 YES YES VT_START DATE 7 NO NO VT_END DATE 7 NO NO

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Constraint
SQL> SELECT table_name, constraint_type, search_condition
FROM user_constraints
WHERE table_name = 'DEPT';
TABLE_NAME CONSTRAINT_TYPE SEARCH_CONDITION
---------- --------------- --------------------------------
DEPT C (VT_START < VT_END) and (VT > 0)

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AS OF PERIOD Query
SQL> SELECT *
2 FROM dept AS OF PERIOD FOR vt DATE '2015-01-01'
3 ORDER BY deptno;
DEPTNO DNAME LOC VT_START VT_END
---------- -------------- ------------- ---------- ----------
10 ACCOUNTING NEW YORK
20 RESEARCH DALLAS
30 SALES SAN FRANCISCO 2014-01-01
40 OPERATIONS BOSTON

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ENABLE_AT_VALID_TIME
LEVEL
-ALL: no filter
-CURRENT: filter records to display currently valid data
-ASOF: filter records to display valid data as of <query_time>
QUERY_TIME
DISABLE_ASOF_VALID_TIME
Clears an ASOF filter
Same as "ENABLE_AT_VALID_TIME('ALL')"
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New Procedures in DBMS_FLASHBACK_ARCHIVE

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No DML Support – Do It Your Self…
SQL> UPDATE dept SET vt_end = DATE '2014-01-01' WHERE deptno = 30;
SQL> INSERT INTO dept (deptno, dname, loc, vt_start)
2 VALUES (30, 'SALES', 'SAN FRANCISCO', DATE '2014-01-01');
SQL> SELECT *
FROM dept
WHERE deptno = 30
ORDER BY vt_start NULLS FIRST;
DEPTNO DNAME LOC VT_START VT_END
---------- -------------- ------------- ---------- ----------
30 SALES CHICAGO 2014-01-01
30 SALES SAN FRANCISCO 2014-01-01

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Temporal validity is supported with Multitenant as of 12.1.0.2
In 12.1.0.1
-DDL and DML works
-Temporal flashback query filters are applied in a non-CDB instance only
No support for temporal joins or temporal GROUP BY
FLASHBACK_QUERY_CLAUSE
Temporal flashback query filters are not applied on views
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Limitations / Assessment

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Core Messages
Native Support for Top-N Queries
There is no good reason for not using it
PL/SQL in SQL Statements
If correctly used, very good feature
Temporal Validity
It’s too soon!
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Questions and answers ...
BASEL BERN BRUGG LAUSANNE ZUERICH DUESSELDORF FRANKFURT A.M. FREIBURG I.BR. HAMBURG MUNICH STUTTGART VIENNA
Christian Antognini Principal Senior Consultant
christian.antognini@trivadis.com
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